Electrical insulators are used to support electrical conductors and/or electrical devices to prevent the loss of electric charge or current therefrom. A typical insulator is constructed from a material which has a very high resistance to electric current so that the electric current does not substantially flow therethrough.
Insulators may be connected to and carried by power lines and/or supports in a variety of ways. For example, high voltage suspension insulators are used to suspend power transmission lines from overhead supports on poles and towers. Boulder suspension insulators are made of strings of porcelain insulators having a size and shape required of that material to provide the necessary mechanical strength, dielectric strength and creapage distance. To provide the necessary mechanical and electrical characteristics, porcelain insulators are typically quite heavy. Moreover, such porcelain insulators are expensive and brittle. Therefore, such porcelain insulators are subject to damage during shipment and insulation.
Overhead electric power lines, wires or conductors are supported by poles or towers which may be constructed of wood, metal or other common materials. The overhead power lines are mounted on poles or towers by insulators which are maintained in a predetermined orientation by an insulator.
These insulators were, in the past, typically constructed of ceramic material such as porcelain, and a variety of shapes and/or designs depending upon the necessary mechanical strength, dielectric strength and leakage distance. However, the use of porcelain for insulators has several disadvantages. For example, porcelain insulators are often very heavy to provide the necessary mechanical and electrical characteristics. Moreover, such porcelain insulators are typically expensive to install and require strong supporting structure for supporting the insulator to the pole or tower. Additionally, porcelain insulators are brittle which makes them subject to being damaged during shipping and installation of the insulators. Porcelain insulators are susceptible to vandalism damage.
Accordingly, in recent years, newer insulators have been developed which include a fiberglass reinforced polymer core and an external protective housing forming annular flanges or webbed weathersheds. The weathershed housing or sheath is usually constructed of an elastomeric or an epoxy material. Elastomer or epoxy sheaths are designed to protect the fiberglass reinforced rods from weather and electrical activity. Weather and electrical activity degrade the mechanical strength of the fiberglass reinforced rod. The weathersheds on the housing intercept water flow down the insulator and increase the distance along the surface of the insulator for better electrical performance in wet or contaminated conditions.
Examples of some prior electrical devices are disclosed in U.S. Pat. No. 1,426,789 to Steinberger; U.S. Pat. No. 1,709,477 to Kyle; U.S. Pat. No. 3,110,759 to Moussou; U.S. Pat. No. 3,483,314 to Harmon; U.S. Pat. No. 3,531,580 to Foster; U.S. Pat. No. 4,243,628 to Herold; U.S. Pat. No. 4,440,975 to Kaczerginski, U.S. Pat. No. 4,476,081 to Kaczerginski et al; U.S. Pat. No. 4,702,873 to Kaczerginski; U.S. Pat. No. 4,714,800 to Atkins et al; U.S. Pat. No. 4,749,824 to Orbeck; U.S. Pat. No. 4,940,857 to Giroux; U.S. Pat. No. 5,220,134 to Novel et al; U.S. Pat. No. 5,147,984 to Mazeika et al; U.S. Pat. No. 5,233,132 to Soucille; U.S. Pat. No. 5,298,301 to Midgley et al; U.S. Pat. No. 5,406,033 to Pazdirek.
In view of the above, there exists a need for an electrical insulator which is reinforced to accommodate the strain from the electrical device or conductor attached to its free end. This invention addresses this need in the prior art as well as other needs which will become apparent to those skilled in the art from this disclosure.